There are two valid ways to ensure leo.roar() exists:

Directly assign a roar function to leo (Option A). Assigning a property to an instance object creates a new method on that instance.

leo.roar = () = > { console.log( ' They\ ' re pretty good! ' ); };

After this, calling leo.roar() is valid.

Copy tony’s properties into leo using Object.assign (Option B). Object.assign(target, source) copies enumerable own properties from the source object into the target object. Since tony.roar exists, executing:

Object.assign(leo, tony);

copies roar into leo, making leo.roar() valid.

Why the other answers are incorrect:

Option C: Object.assign(leo, Tiger) copies properties from the function object Tiger , not from Tiger.prototype and not from a Tiger instance. Tiger (the function) has no roar property, so nothing useful is copied.

Option D: leo.prototype is undefined because leo is an instance, not a constructor function. Only constructor functions have a .prototype property. This line would cause an error.

JavaScript Knowledge References (text-only)

Instances have their own properties and do not contain a .prototype property.

Object.assign(target, source) copies own enumerable properties of the source object.

Assigning a function as a property of an object creates a callable method.

==================================================